Cellulose ether composition



V/lscos//y cen #po/ses x/OOO -f Dc. 5, '19671.

w. c. CHAMBERS 'ET/AL 3,356,519

\ OELLULOSE ETHER. COMPOSITION Filed Feb. 28, 1964 0./ g/yoxa//rea/ed e//aer @Ossa/ved a/,o//S

United States Patent() 3,356,519 CELLULOSE ETHER COMPOSITION William C. Chambers, Plaquemine, and Milford Lee,

Baton Rouge, La., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Feb. 28, 1964, Ser. No. 348,023 1 Claim. (Cl. 106-187) The present invention relates to novel cellulose ether lcompositions and particularly surface treated cellulose ether compositions modified to achieve improved solution properties. ,Y

It is known that the surface treatment of water-soluble cellulose ethers with a cross-linking material such as aldehyde or dialdehyde improves the dispersibility of that ether in water. When mixed with water, ethers without such treatment tend to agglomerate, thereby forming difiicultly soluble gels, which interfere with the usefulness of the ethers as dispersants and thickeners for aqueous systems. The surface treated ethers are readily dispersed in aqueous systems, but com-plete solution of such ethers, as evidenced by the attainment of a stable solution .vis. cosity, may be significantly delayed. As the amount of the surface treating agent applied to the ether is increased, the dispersibility of the resulting product is enhanced, but at the same time the solution rate of the ether is retarded.

A further characteristic of such surface treated ethers is their tendency to manifest a false viscosity immediately after dissolution in water. By this is meant the initial viscosity manifested by the solution gives way to a substantially lower viscosity over a period of time which may take as long as several hours. When the intended purpose of the cellulose ether is that of a thickening agent, such initial false thickening often leads to erroneous results in the utilization of the ethers as thickeners. Even when the phenomenon is understood and taken into account in determining dosage, process control is diflicult to achieve.'

In view of the foregoing considerations, it would be desirable, and it is an object of the present invention, to provide a novel process and composition whereby surface treated cellulose ethers are more readily dissolved subsequent to dispersion in water. A further and equally important object istonprovide surface treated cellulose ether compositions which'quickly produce a true viscosity as' the ether is dissolved. These, and other objectsand benets as will become apparent hereinafter, are accomplished in the present invention. Y

The present invention involves the discovery that water-soluble cellulose ethers, having a surface treatment with an aldehydic material to render the ethers more readily dispersible in water, manifest improved solution properties when utilized in conjunction with certain buffering agents. Particularly, a sufficient amount of one or more of such agents is incorporated into an intimate admixture with the surface treated, water-soluble cellulose ethers to produce, when the admixture is dissolved in water, a solution pH within the range of about 7.5 to about 9.5. Within this relatively narrow pH range a surface treated cellulose ether is characterized by an increased solution rate in Water. Further the tendency of the surface treated ether to develop false solution viscosities is diminished if not completely obviated. While the above advantages are also obtained at a pH greater than about 9.5, the energy required to disperse the ether in water begins to increase rapidly with further increases in pH.

The invention is applicable to those water-soluble cellulose ethers having an aldehydic surface treatment as described by Menkart et al. in United States Patent 3,072,- 635 and ethers of like nature described by Jullander in United States Patent 2,879,268. Particularly, the cellulose 'ethers described in the former patent as being suitable 'for surface treatment include the various water-soluble and alkali-soluble, non-ionic and ionic ether derivatives of cellulose. Beginning with line l0 in column 2 of this patent are detailed references to such ethers. The Jullander patent also contains teachings of such ethers.

The surface treatment of the cellulose ethers encompassed by the present invention includes the application to -the particulate ether of any aldehydic material, preferably a dialdehyde containing less than 6 carbons such as, for example, formaldehyde, and a variety of lower aliphatic dialdehydes such as glyoxal, pyruvaldehyde, malonaldehyde, succinaldehyde, adipaldehyde and the like materials. Excellent results are achieved if the present invention is practiced with water-soluble ether products on which surface treatment has been accomplished by the spraying of the dry particulate cellulose ether with a liquid dispersion of glyoxal, formaldehyde or pyruvaldehyde in an inert solvent. While the surface treatment must be applied to the ethers existing as particulate solids, either powdered or granulated forms are operable.

Having obtained a surface treated, water-soluble cellulose ether, the ether is dry blended in accordance with the invention with an alkali metal or ammonium salt of a weak protonic acid. Typical salts are the alkali metal salts and acid salts of such acids as carbonic, phosphoric, boric, acetic and citric acids. The amount of one or more of such salts added to the ether composition is that sufiicient to produce, upon dissolution of the admixture in water, a pH within the range from about 7.5 to about 9.5. While the above-indicated order of treatment, i.e., surface treatmentfirst and then butferingagent, is preferred, the addition of the buering salts may also take place during or after operations carried out to effect surface treatment of the ether.`

The following examples illustrate the mode of carrying out the invention, as the invention is presently understood. It should be understood, however, that specific proportions and reaction conditions utilized therein are not intended as limitations on the invention other than as delineated by the claims.

was charged to an operating ribbon blender wherein it was subjected to a ne spray of glyoxal dispersed in a `liquid surface active, kpolyoxyalkylene glycol ether. A

suicient lamount of this mixture was applied'to give the ether a surface treatment of 0.1 percent glyoxal and 1 percent of the polyoxyalkylene glycol ether. In a second series of runs, sutlicient sodium borate (Na2B4OfV10H2O) was blended with the ether during the spraying operation to provide 0.2 percent by weight of the inorganic buffering addita-ment in addition to the surface treatment with glyoxal in polyoxyalkylene glycol ether as described above. Unless otherwise specified, all percentages herein are based on the weight of the dry cellulose ether.

The modified, surface treated cellulose ether compositions were evaluated las to their dispersibility by Iadding 10 grams of each ether to 300 grams of water at 20 C. and a pH of 7. After allowing the ether to stand in the water for 30 seconds, the mixture was stirred slightly to determine the extent of solids agglomeration A rating of excellent was given those dispersions having no visible agglomerates. In other words, dispersion of the ether in water resulted in a clear solution visually free of any agglomerates, i.e., occluded and poorly wetter ether solids.

The method used for determining the solution time or the solution rate of the modiiied ethers involved the following procedure. Nine hundred and eighty grams of distilled water at a pH of 7 was added to a 1,500 milliliter a manner similar t-o the procedure described in Example l for determining solution rates. These rates were determined for solutions made up to contain 2 percent by weight of the ether. A plot of the resulting data is shown beaker. The water temperature was adjusted to C. 5 in l[he attached drawing Af arjgperteg stllflfer Pfovldg gltattlln' o?? mllhller It will be observed that the ether solution developed lfloarrlnixriguaieilijt Oheartafitlezi's aZOte) gtriamse Xia e'aufae a false viscosity somewhat in proportion to theextent moded ether'to be evaluated' was added The spindle of glyoxal treatment of the dissolved ether. This viscosity of a Brookfield viscosi-meter was then lowered into the @sied tor a period of time up '0.35 minutes after mmal dispersion of the cellulose ether in water at a `pH of 7. resulting dispersion of the ether and readings of the solu- However at a solution H of 9 both of the Surface tion viscosity taken every 60 seconds for the first 10 d h d minutes after addition of the ether, agitation of the solutieate et er pro iets fo .0W essentially the stime .S019 tion being stopped while the readings were made. Subsenon rate cufve which achlajved a mlxlmum viscosity m quent to the first 10 minutes, the viscosity readings were 15 about 2Q mmfltes and remained at this level. made at 5 vminute intervals until the solution achieved what 1s claimed 1S: an essentially constant viscosity for at least 3 consecutive A Composition 0f matter Consisting essentially 0f a readings. This viscosity plateau was assumed to indicate Water-SOlUble, Particulate celluloSe ether liaVing Ian aide* the achievement of complete dissolution of the ether. hydie Surface treatment t0 increase the diSPefSibility 0f The results of the dispersibility and solution time dethe ether in Water and an alkali metal Salt 0f a Weak terminations are listed in the following table according PfOtOniC acid in lan aInOUnt Sullcieient t0 maintain an to the particular water-soluble cellulose ether composiaqueous solution of the ether and said salt in water at tion evaluated a pH within the range from about 7.5 to about 9.5.

TABLE I Dlspersibillty Soillltgrtgslne Cellulose Ether Without With Without with NaiBiOv NaqBiOy Borate Borate Metgiyl ce1lulos e. .gm. Excelent Excelent.... fditiiiiuioief.;:i: :iiiidoiiii: d0 60 10 It will be observed that excellent dspersibility was References Cited achieved in all instances and when the surface treated UNITED STATES PATENTS ethers contained a basic buffering agent in accordance 1775179 9/1930 Weidig 106 184 with the invention, eg., the sodium borate hydrate illus- 216632989 12/1953 Schlatte' trated, the time required to achieve Complete S0lUt10n 0f 2,334,777 5/1958 Juuander 260 232 the ether was substantially diminished- 2,842,451 7/1958 Grummitt et ai 26o-232 2,879,268 3/1959 Jullander 260-232 EXAMPLE 2 45 3,072,635 1/1963 Menkart et .ai 26o-232 Two aliquots of a water-soluble methyl cellulose ether grvigs et al 252 363 5 were sprayed with suflicient glyoxal to provide a glyoxal n surface treatment for each of the ether aliquots of 0.1 OTHER REFERENCES and 0.2 percent by weight of the ether, respectively. Handbook of Chemistry Iand Physics, Hodgman et al. Spraying of the cellulose ether was accomplished as the by Chemical Rubber Pub. C0., 40th ed., 1959, pp. ether was `continuously -agitated in a small ribbon blender. 1721-22. Subsequently, the aliquots of surface treated ether were ALEXANDER H BRODMERKEL Primary Examineh aged for 4 months at ambient room temperatures. 55

Each of the treated aliquots was evaluated for its solution rate in water at a pH of 7 and again at a pH of 9 in ROBERT F. WHITE, Examiner.

I. H. WOO, Assistant Examiner. 

